The Royal Society has placed an archive of their journals online. The archive covers papers published fro 70 years ago to their earliest, which dates to 1665. The archived documents are freely available. As they explain in their announcement of the new online archive:

The Royal Society is the world’s oldest scientific publisher, with the first edition of Philosophical Transactions of the Royal Society appearing in 1665. Henry Oldenburg – Secretary of the Royal Society and first Editor of the publication – ensured that it was “licensed by the council of the society, being first reviewed by some of the members of the same”, thus making it the first ever peer-reviewed journal.

Philosophical Transactions had to overcome early setbacks including plague, the Great Fire of London and even the imprisonment of Oldenburg, but against the odds the publication survived to the present day. Its foundation would eventually be recognised as one of the most pivotal moments of the scientific revolution.

I found myself just plugging a random year into the archive's search engine and browsing the titles for articles of interest. In many ways I found the obscure papers more interesting than the historical ones because they reveal a scope of curiosity that is truly astonishing.